Seven stereoisomers of the potential anti-HIV drug "Castanospermine" (1) will be synthesized via sequences which begin with new enzyme-catalyzed reactions. These preparations are designed to be: (i) cheap and amenable to large scale production, and: (ii) asymmetric, providing either enantiomer of the product. Samples of the compounds produced will be screened for anti-HIV activity and for inhibition of glycosidases (See Appendices). Structure-activity relationships for epimers of Castanospermine are as follows: 1-Epicastanospermine, 8a-Epicastanospermine, 1.7- Diepicastanospermine, 7.8a-Diepicastanospermine, 1.8a- Diepicastanospermine, S.s-Diepicastanospermine, and 7- Epicastanospermine.